A Fundamental Investigation of Threshold Stress in Dispersion-Strengthened Materials

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The project is aimed at developing a quantitative model for high temperature creep of dispersion strengthened aluminum alloys (Al-Sc-Mg-Zr-SiC) by integrating the dislocation dissociation and positive climb concepts. An innovative creep specimen geometry will elucidate the threshold stress mechanisms and the microstructural evolution during creep deformation. An understanding of the influence of particle size and distribution on threshold stress and creep kinetics can lead to development of high temperature aluminum alloys by microstructural design. The development of quantitative model based on fundamental dislocation parameters is in dire need. Major goals of the study are: (1) to investigate the deformation characteristics in simpler alloy systems (Al-Sc, Al-Zr, etc) for a systematic understanding of their mechanical behavior; (2) to perform in-situ transmission electron microscope (TEM) straining experiments for determining dislocation velocities during their glide and climb movements; and (3) to develop quantitative model using the experimentally determined parameters. The work involves a combination of university-industry-government laboratory-national user facility.%%%This research develops new understanding of the fundamental mechanisms of dispersion strengthening beyond the current state of the art. The results are aimed at the development of creep-resistant materials for high-temperature applications in various technologies.***